Phosphor, light-emitting apparatus including the same, and phosphor production method

ABSTRACT

A phosphor is provided which is represented by the general formula M x Ce y Pr z Si 6 N 8+w . M is at least one element selected from the group consisting of La, Y, Tb and Lu. And x, y, z and w satisfy 2.0&lt;x&lt;3.5, 0&lt;y&lt;1.0, 0&lt;z&lt;0.05, and 2.0&lt;w&lt;4.0, respectively.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a phosphor, a method of producing thephosphor, and a light emitting apparatus including the phosphor; andmore particularly to a nitride phosphor that is composed of anitrogen-containing compound and can emit light in a green-to-yellowrange, a light-emitting apparatus including the nitride phosphor, and amethod for producing the nitride phosphor.

2. Description of the Related Art

Light-emitting apparatuses have been developed which include a lightsource, and a wavelength conversion member that is excited by light fromthe light source and can emit different color light from that of thelight source. As a result, the light-emitting apparatuses can emit lightin various colors based on the principle of additive light color mixing.For example, a light-emitting device emits the primary light in a shortwavelength range corresponding to a range from ultraviolet to visiblelight so that a phosphor is excited by this emitted light. Accordingly,the primary light is at least partially converted into light having adifferent wavelength from the primary light. As a result, desired light(e.g., red, blue, green or the like) can be provided. Also, white lightcan be provided by additive color mixture of different light components.

Based on the principle, LED lamps have been used which includelight-emitting diodes (hereinafter, referred to as LEDs) for many fieldssuch as signal light, mobile phone, various types of illuminations,vehicle indicator, or various types of display apparatuses. Inparticular, with the increasing application of white LED light-emittingapparatuses including an LED and a phosphor to liquid crystal display(LCD) backlight, electronic flash, and the like, the use of the whiteLED light emitting apparatuses has increased. In addition, recently, thewhite LED light-emitting apparatuses are tried to be used as a lightingapparatus. Since the white LED light-emitting apparatuses haveadvantages such as long life and being mercury-free, in order to reducethe environmental load, it is expected that the white LED light-emittingapparatuses can serve as a replacement light source for a fluorescentlamp.

A light-emitting apparatus including a white LED includes a blue LED anda yellow phosphor (for example, see Japanese Patent Publication No. JP3,503,139 B). This light-emitting apparatus mixes blue light emittedfrom the LED with yellow light that is converted from the blue lightfrom the LED by the yellow phosphor, whereby emitting white light. Inthis case, the phosphor used in this light-emitting apparatus isrequired to be efficiently excited by blue light with a wavelength from420 to 470 that is emitted by the LED, and to emit light in a yellowrange.

Also, the LED light-emitting apparatus is actively studied to increaseits light emission properties. For example, in order to increase thebrightness of white light, it is important to increase the intensitiesof both the light components for different colors. For this reason, aphosphor is required which can convert the primary light from the LED ata high energy efficiency. In addition, in order to improve the colorrendering property or color purity of white light, it is important thatthe light components have designed colors. To achieve this, the phosphoris required to have its peak wavelength in a predetermined wavelengthrange.

An yttrium aluminum garnet group phosphor activated by cerium is knownas a yellow phosphor. Also, it is known that Y of this yellow phosphorcan be partially substituted by Lu, Tb, Gd or the like, or Al of thisyellow phosphor can be partially substituted by Ga or the like. Thelight wavelength of the yttrium aluminum garnet group phosphor activatedby cerium can be widely adjusted by adjustment of composition.

In addition, as for phosphors other than these oxide phosphors, nitridephosphors are also known which have properties different from otherinorganic compounds. In particular Si₃N₄, AlN, BN, GaN, and the like areused in a variety of applications such as substrate materials,semiconductors, light-emitting diodes, and are industrially produced.Also, nitride phosphors including three or more elements have beenwidely studied in recent years. Some nitride compounds were reportedwhich were excited by a blue LED or near-ultraviolet LED, and emittedlight in a blue-to-red range.

Since the compounds or phosphors have different light emissionspectrums, in the case where two or more of these compounds or phosphorsare used, the white LED light-emitting apparatuses may have furtherimproved properties. For example, in the case where a (Sr, Ca)AlSiN₃:Euphosphor as a nitride group phosphor is used in the white LEDlight-emitting apparatus disclosed in JP 3,503,139 B, the colorrendering property and the color reproduction range can be improved (forexample, see Japanese Patent Laid-Open Publication No. JP 2006-8,721 A).

Also, in the case the yttrium aluminum garnet group phosphor activatedby cerium capable of emitting a yellow light component is replaced bysome other phosphors, the color rendering property and the colorreproduction range can be improved.

For example, La₃Si₆N₁₁:Ce is disclosed as one of the some otherphosphors (e.g., see Japanese Patent Laid-Open Publication No. JP2008-88,362 A).

The present invention is devised to solve the above problems. It is amain object of the present invention to provide a phosphor that includesa particular compound for increasing the red light component whilekeeping the green light component high as compared with La₃Si₆N₁₁:Ce, amethod for producing this phosphor, and a light-emitting apparatusincluding this phosphor.

SUMMARY OF THE INVENTION

A phosphor according to one aspect of the present invention includes acompound that is represented by the general formulaM_(x)Ce_(y)Pr_(z)Si₆N_(8+w). M is at least one element selected from thegroup consisting of La, Y, Tb and Lu. And x, y, z and w satisfy2.0<x<3.5, 0<y<1.0, 0<z<0.05, and 2.0<w<4.0, respectively.

A light-emitting apparatus according to another aspect of the presentinvention includes an excitation light source, the aforementionedphosphor as a first phosphor, and a wavelength conversion member. Theexcitation light source can emit light in a range from ultraviolet toblue light. The first phosphor can absorb a part of the light from theexcitation light source, and can emit luminescent radiation. The firstphosphor is distributed in the wavelength conversion member.

A phosphor production method according to still another aspect of thepresent invention includes a preparation pulverization and mixture step,a filling and burning step, and a solid-liquid separation, drying,pulverization, dispersion and filtering step. In the preparationpulverization and mixture step, materials for elements to compose acomposition of phosphor as the elements themselves, or oxide, nitride orcarbonate of the elements, are prepared, pulverized, and mixed. In thefilling and burning step, a crucible is filled with the obtainedmaterials, and the obtained materials are burned in a reducingatmosphere. In the solid-liquid separation, pulverization, dispersionand filtering step, the burned product is subjected to solid-liquidseparation, and the product after the solid-liquid separation is dried,pulverized, dispersed and filtered so that phosphor powder is obtained.The composition of the phosphor is represented by the general formulaM_(x)Ce_(y)Pr_(z)Si₆N_(8+w). M is at least one element selected from thegroup consisting of La, Y, Tb and Lu. And x, y, z and w satisfy2.0<x<3.5, 0<y<1.0, 0<z<0.05, and 2.0<w<4.0, respectively.

According to the present invention, it is possible to increase the redlight component while keeping a green light component high.

The above and further objects of the present invention as well as thefeatures thereof will become more apparent from the following detaileddescription to be made in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view showing a light-emitting apparatusaccording to an embodiment of the present invention;

FIG. 2 is a graph showing the light emission spectrums of phosphorsaccording to examples 1 to 4 of the present invention, and a comparativeexample 1;

FIG. 3 is a graph showing the excitation spectrums of the phosphorsaccording to the examples 1 to 4 of the present invention, andcomparative example 1;

FIG. 4 is a SEM (scanning electron microscope) image of the phosphoraccording to the example 4 of the present invention magnified by 1,000times;

FIG. 5 is a graph showing the normalized light emission spectrums ofphosphors according to examples 4 to 5 of the present invention, andcomparative examples 2 to 3;

FIG. 6 is a graph showing the excitation spectrums of the phosphorsaccording to the examples 4 to 5 of the present invention, and thecomparative examples 2 to 3;

FIG. 7 is a graph showing the normalized light emission spectrums ofphosphors according to the examples 4 and 6 to 7 of the presentinvention, and the phosphor according to the comparative example 4;

FIG. 8 is a graph showing the excitation spectrums of the phosphorsaccording to the examples 4 and 6 to 7 of the present invention, and thecomparative example 4;

FIG. 9 is a graph showing the light emission spectrums of a lightemitting apparatus according to the comparative example 1 and theexample 3 of the present invention; and

FIG. 10 is an enlarged graph of a range from 0 to 1,500 in lightemission intensity in FIG. 9.

DETAILED DESCRIPTION OF THE EMBODIMENT(S)

The following description will describe embodiments according to thepresent invention with reference to the drawings. It should beappreciated, however, that the embodiments described below areillustrations of a phosphor, a method for producing the phosphor and alight emitting apparatus that includes the phosphor to give a concreteform to technical ideas of the present invention; and a phosphor, amethod for producing the phosphor and a light emitting apparatus thatincludes the phosphor of the present invention are not specificallylimited to the description below.

A phosphor according to an embodiment of the present invention includesa compound that is represented by the general formulaM_(x)Ce_(y)Pr_(z)Si₆N_(8+w). M is at least one element selected from thegroup consisting of La, Y, Tb and Lu. And x, y, z and w satisfy2.0<x<3.5, 0<y<1.0, 0<z<0.05, and 2.0<w<4.0, respectively. It is morepreferable that x, y and z satisfy 2.0<x<3.0, 0<y<0.5, 0<z<0.03,respectively.

Also, in a phosphor according to another embodiment, the phosphorabsorbs light in a range from ultraviolet light to visible blue lightand emits light different from the absorbed light, and the light emittedby the phosphor has a light emission spectrum including first and secondpeaks. The wavelengths of the first and second peaks fall within rangesfrom 515 to 545 nm, and 610 to 620 nm, respectively.

Also, in a phosphor according to another embodiment, the light emissionintensity ratio (I_(p2)/I_(p1)) of the second light-emitting peakrelative to the first light-emitting peak is defined in the emissionspectrum. The light emission intensity ratio satisfies0.56<I_(p2)/I_(p1).

Since the aforementioned phosphor contains Pr, it is possible toincrease the light emission intensity in the wavelength range from 610to 620 nm. As a result, it is possible to increase a red lightcomponent, whereby improving a color rendering property.

Also, in a phosphor according to another embodiment, the phosphor canfurther contain fluorine. In this embodiment, the content of fluorinefalls within a range from 10 to 10,000 ppm.

Also, in a phosphor according to another embodiment, the phosphor canfurther contain oxide. In this embodiment, the content of oxide fallswithin a range from 100 to 10,000 ppm.

Also, in a phosphor according to another embodiment, it is preferablethat the phosphor have a crystal phase, the percentage of which is notless than 50% by weight.

Also, a light-emitting apparatus according to another embodiment caninclude the aforementioned phosphor as a first phosphor, and at leastone second phosphor that can absorb at least a part of the light fromthe excitation light source, and can emit luminescent radiation with apeak wavelength different from that of the first phosphor.

Also, in a phosphor production method according to another embodiment,the burned product can be placed in acid solution, whereby reducing thecontent of impurities contained in the burned product.

Also, in a phosphor production method according to another embodiment,the acid solution can contain hydrochloric acid.

Also, in a phosphor production method according to another embodiment,it is preferable that the phosphor further contains fluorine. Thecontent of fluorine in the produced phosphor preferably falls within arange from 10 to 10,000 ppm. The reason is to provide a sufficient fluxeffect without adverse effect on the properties of the phosphor.

Since the phosphor contains fluorine as flux, it is possible to increasethe reactivity of the material for the phosphor according to the presentinvention.

In the description of the present invention, a relationship betweencolor name and chromaticity coordinates, a relationship between lightwavelength range and monochromatic light, and the like are based on theJIS standard (JIS Z8110). Specifically, a range of 380 to 455 nmcorresponds to the bluish violet color, a range of 455 to 485 nmcorresponds to blue, a range of 485 to 495 nm corresponds to bluishgreen, a range of 495 to 548 nm corresponds to green, a range of 548 to573 nm corresponds to yellowish green, a range of 573 to 584 nmcorresponds to yellow, a range of 584 to 610 nm corresponds to apricot,and a range of 610 to 780 nm corresponds to red.

EMBODIMENT(S)

A phosphor according to an embodiment contains silicon and nitrogen, andactivated by Ce and Pr. The phosphor can absorb light in an ultravioletto blue range, and emit light. The phosphor is represented by thefollowing general formula.

M_(x)Ce_(y)Pr_(z)Si₆N_(8+w)

where M is at least one element selected from the group consisting ofLa, Y, Tb and Lu, and x, y, z and w satisfy 2.0<x<3.5, 0<y<1.0,0<z<0.05, and 2.0<w<4.0, respectively.

More preferably, x satisfies 2.0<x<3.3, and most preferably 2.0<x<3.0.The reason to set the lower limit of the x range is to efficientlyobtain the target composition of phosphor. For example, in the casewhere the target composition of phosphor is La₃Si₆N₁₁, unintendedLaSi₃N₅ may be produced. In this case, a classification process or otherprocess is additionally required to separate the target composition ofthe phosphor from the other composition. Contrary to this, according tothe present invention, since x satisfies the above range, adjustment ofthe composition of phosphor can simply increase the probability that thetarget composition of phosphor will be obtained without time and effort.Also, the reason to set the upper limit of the x range is to preventwaste of La, since even if La is added more than the upper limit anexcess amount of La over the upper limit hardly contributes toproduction of the target composition of phosphor.

Also, y more preferably satisfies 0<y<0.8, and most preferably 0<y<0.5.Although a certain amount of Ce is required to provide light emission atthe target wavelength, if the amount of Ce is too much, Ce elements asactivator will interfere with each other, which in turn may reduce thelight emission intensity of the phosphor. The reason to define the yrange is to prevent the reduction of the light emission intensity of thephosphor.

Also, z more preferably satisfies 0<z<0.04, and most preferably0<z<0.03. Although a certain amount of Pr is required to increase a redlight component, if the amount of Pr is too much, Pr, which also servesas an activator, will disturb light emission of Ce, which in turn mayreduce the entire light emission intensity of the phosphor. The reasonto define the z range is to prevent the reduction of the entire lightemission intensity of the phosphor.

For example, when light emission intensity (I_(p615)) at 615 nm isdefined relative to light emission intensity (I_(p535)) at 535 nm, thisphosphor provides relative light emission intensity0.56<I_(p615)/I_(p535) in light emission when absorbing light in a rangefrom ultraviolet to blue light.

In addition, it is preferable to add a flux compound to one or more ofthe materials for the phosphor, so that the flux compound is brought inas a liquid at a burning temperature. Also, it is preferable that theburned product be placed in an acid solution, whereby reducing thecontent of impurities contained in the obtained product.

Also, it is preferable that the phosphor be at least partiallycrystallized. For example, if the phosphor is in a vitreous (amorphous)state, the component ratio of the phosphor will be uneven. The reason isthat the structure in a vitreous state does not have a regulararrangement. As a result, the phosphor in the vitreous state may produceuneven color light. In order to avoid this, it is necessary to providehighly uniform reaction conditions in production processes. On the otherhand, since the phosphor according to this embodiment can be powder orgranular matter that is not in a vitreous phase but in a crystallinephase, the phosphor can be easily produced and be easily subjected totreatment. In addition, this phosphor can be uniformly dissolved inorganic solvent. Accordingly, a luminescent plastic or polymer thin filmcan be easily adjusted. Specifically, the percentage of crystal phase inthe phosphor according to this embodiment preferably falls within arange not less than 50% by weight, and more preferably not less than80%. This percentage corresponds to the percentage of crystal phase inthe phosphor capable of emitting light. In the case where the percentageof crystal phase in the phosphor is not less than 50%, luminescentradiation of the phosphor can be practically used. From this viewpoint,the phosphor preferably has a percentage of crystal phase as high aspossible. In this case, the light emission intensity of the phosphor canbe high, and the phosphor can be more easily subjected to treatment.

(Particle Diameter)

It is preferable that the particle diameter of the phosphor falls withina range 1 to 50 μm, and more preferably 2 to 30 μm in terms of use inthe light-emitting apparatus. In addition, it is preferable that thepercentage of the phosphor with the above mean particle diameter behigh. Also, the particle size distribution is preferably narrow. In thecase where a phosphor is used which has less unevenness of particlediameter or particle size distribution, and has a large particlediameter and excellent optical properties, color unevenness can bereduced. Therefore, it is possible to provide a light-emitting apparatuswith excellent color tone. Accordingly, in the case where the phosphorhas a particle diameter in the above range, light absorption andconversion efficiencies can be high. A phosphor with a particle diameterless than 2 μm is likely to form an aggregate.

(Production Method)

The following description will describe a method for producing thephosphor according to this embodiment. Materials for elements to composethe composition of the phosphor according to this embodiment can be theelements themselves, or oxide, carbonate, nitride or the like of theelements. These materials are measured to provide a predeterminedcomposition ratio. Additives such as flux can be suitably added to thematerials.

Specifically, it is preferable to use nitride or oxide of Si in thecomposition of the phosphor as a material for the phosphor. However,imide, amide or other compound of Si also can be used. Examples of thematerial of Si is provided by Si₃N₄, SiO₂, Si(NH)₂, and the like.However, in the case where Si itself is used alone, the nitride phosphorcan be inexpensively produced, and can have good crystallinity. Thepurity of the material is preferably 2N or more. However, the materialmay contain other elements such as Li, Na, K, B. Also, Si can also bepartially substituted by Al, Ga, In, TI, Ge, Sn, Ti, Zr, or Hf.

Also, it is preferable to use nitride, oxide or the like of La in thecomposition of the phosphor as a material for the phosphor. However,other compounds of La or La itself can be used. Examples of the materialfor La can be provided by LaN, La₂O₃, LaSi, LaSi₂ and the like. Thepurity of the material is preferably 2N or more. However, the materialmay contain other rare earth elements. Also, it is preferable to usenitride, oxide or the like of Ce and Pr in the composition of thephosphor as materials for activators of the phosphor. However, othercompounds of Ce and Pr, or Ce and Pr themselves can be used. Examples ofother materials for Ce and Pr can be provided by halide, carbonate,phosphate, silicate, and the like of Ce and Pr. In particular, it ispreferable that cerium fluoride, which is a fluoride, be used as amaterial for Ce as activator. The reason is that cerium fluoride servesnot only as material of the phosphor, but also as a flux.

The materials can be mixed in a dry or wet manner by a mixer. Thematerials can be mixed by a pulverizer as a mixer for increasing thespecific surfaces of the materials. Ball mills are widely used as apulverizer in commerce. In addition to ball mills, vibration mills, rollmills, jet mills, mortars and pestles, or the like can be used as thepulverizer. Also, the materials can be mixed by a pulverizer and a mixersuch as ribbon blender, V-type blender, and Henschel mixer. In orderthat the specific surfaces of the materials may fall within certainranges, the materials can be classified by a wet separator such as asettling tank, hydrocyclone or centrifuge, or a dry classifier such as acyclone or air separator. These wet separators and dry classifiers arewidely used in commerce. Materials that are unstable in the air aremixed in an argon or nitrogen atmosphere in a glove box.

The aforementioned mixed materials are placed in a crucible such as aSiC, quartz, alumina or BN crucible, and are burned in a reducingatmosphere of N₂ and H₂. The burning atmosphere may be an argon,ammonia, carbon monoxide or hydrocarbon atmosphere, or the like. Thematerials are burned at a temperature in a range from 1,000° to 2,000°C. for 1 to 30 hours. The burning pressure is set to a pressure in arange from atmospheric pressure to 10 atmospheres. The materials can beburned by tubular furnace, high-frequency furnace, metal furnace,atmosphere furnace, gas-heating furnace, or the like.

The target phosphor powder is obtained by pulverization, dispersion,filtration and the like of the burned product. The target phosphorpowder is subjected to solid-liquid separation. Solid-liquid separationis conducted by filtration, suction filtration, pressure filtration,centrifugal separation, decantation, or the like, which is widely usedin commerce. The target phosphor powder can be dried by vacuum dryer,heating dryer, conical dryer, rotary evaporator, or the like, which iswidely used in commerce. In addition, in order to remove parts otherthan the target crystal phase, the target phosphor powder can be placedin an acid solution. In this case, it is possible to further improve thelight emission efficiency.

(Light-Emitting Apparatus)

The following description describes a light-emitting apparatus 100 (seeFIG. 1) according to this embodiment that includes the phosphor. Forexample, a lighting apparatus (e.g., fluorescent lamp), a displayapparatus (e.g., display and radar), LCD, and the like can be used asthe light-emitting apparatus. It is preferable to use a light-emittingdevice that emits light in a range from near-ultraviolet light toshort-wavelength visible light as the excitation light source. Inparticular, semiconductor light-emitting devices can be small and highlyeffective in power consumption, and can emit vivid color light.Mercury-vapor lamps or the like, which are used for existing fluorescentlamps, can be also suitably used as another excitation light source.

Various shapes of light-emitting apparatuses including a light-emittingdevice are known, such as so-called bullet type and surface-mount typelight-emitting apparatuses. The light emitting apparatus according tothis embodiment, which is a surface-mount type light-emitting apparatus,is now described with reference to FIG. 1.

FIG. 1 is a schematic view showing the light-emitting apparatus 100according to this embodiment. The light-emitting apparatus 100 accordingto this embodiment includes a package 110 that has a recessed portion, alight-emitting device 101, and a sealing member 103 that covers thelight-emitting device 101. The light-emitting device 101 is arranged onthe bottom surface 112 of the recessed portion of the package 110, andis electrically connected by conductive wire lines 104 to a pair of leadterminals (positive/negative lead terminals) 111 that are arranged inthe package 110. The recessed portion is filled with the sealing member103, which is formed of resin containing the phosphor 102. End parts ofthe positive/negative lead terminals 111 protrude from outside surfacesof the package 110, and are bent so that the end parts extend along theexterior shape of the package 110. The light-emitting apparatus 100 issupplied with electric power through the lead terminals 111 from theoutside, whereby emitting light. The following description will describecomponents of the light-emitting device according to this embodiment.

(Light-Emitting Device 101)

The light-emitting device 101 can emit light in a range from ultravioletto visible light. The peak wavelength of light emitted by thelight-emitting device 101 preferably falls within a range from 240 to520 nm, more preferably from 420 to 470 nm. For example, a nitridesemiconductor device (In_(x)Al_(y)Ga_(1-x-y)N, 0≦x, 0≦y, x+y≦1) can beused as the light-emitting device 101. In the case where a nitridesemiconductor device is used, it is possible to provide amechanical-shock-resistant, stable, light-emitting apparatus.

(Phosphor)

The phosphor 102 according to this embodiment is distributed in a partof the sealing member 103. According to this embodiment, the sealingmember serves not only as a member for protecting the light-emittingdevice and the phosphor from the external environments, but also as awavelength conversion member. In the case where the sealing memberincluding the phosphor is arranged in proximity to the light-emittingdevice 101, the light from the light-emitting device 101 can beefficiently converted into light with a different wavelength from thelight from the light-emitting device. As a result, it is possible toprovide a light-emitting apparatus with good light emission efficiency.However, the member including the phosphor is not limited to be arrangedin proximity to the light-emitting device. In consideration of influenceof heat on the phosphor, the wavelength conversion member containing thephosphor can be spaced at a certain interval from the light-emittingdevice. Also, the phosphor 102 can be mixed in the sealing member 103 ata substantially even ratio, whereby reducing color unevenness of light.

Also, two or more types of phosphors 102 can be used. For example, thelight-emitting apparatus 100 according to this embodiment can includethe light-emitting device 101 for emitting blue light, the phosphoraccording to the embodiment excited by the blue light, and the phosphorfor emitting red light. In this case, the light-emitting apparatus canemit white light with good color rendering. Examples of the phosphor foremitting red light to be used together with the phosphor according tothis embodiment can be provided by nitride phosphors such as(Ca_(1-x)Sr_(x)) AlSiN₃:Eu (0≦x≦1.0) and(Ca_(1-x-y)Sr_(x)Ba_(y))₂Si₅N₈:Eu (0≦x≦1.0, 0≦y≦1.0), halide phosphorssuch as K₂(Si_(1-a-b)Ge_(a)Ti_(b))F₆:Mn (0≦a≦1, 0≦b≦1). In the casewhere these phosphors for emitting red light are used together with thephosphor according to this embodiment, components corresponding to threeprimary colors can have wide half-value widths. As a result, thelight-emitting apparatus can emit warm white light.

Other examples of the phosphors for emitting red light to be usedtogether with the phosphor according to this embodiment can be providedby oxysulfide phosphors activated by Eu, such as (La, Y)₂O₂S:Eu, sulfidephosphor activated by Eu, such as (Ca, Sr)S:Eu, halophosphate phosphorsactivated by Eu and Mn, such as (Sr, Ca, Ba, Mg)₁₀(PO₄)₆Cl₂:Eu, Mn,oxide phosphors activated by Ce such as Lu₂CaMg₂(Si, Ge)₃O₁₂:Ce, andoxynitride phosphors activated by Eu, such as α-SIALON phosphor.

Also, a green or blue phosphor can be used together with the phosphoraccording to this embodiment. In the case where a phosphor is addedwhich emits green or blue light with a peak wavelength slightlydifferent from the phosphor according to the present invention, thecolor reproduction range and the color rendering property can be furtherimproved. Also, in the case where a phosphor is added which absorbsultraviolet light and emits blue light, a light-emitting device thatemits ultraviolet light can be used instead of the light-emitting devicethat emits blue light, so that the color reproduction range and thecolor rendering property are improved.

Examples of the phosphors for emitting green light to be used togetherwith the phosphor according to this embodiment can be provided bysilicate phosphors such as (Ca, Sr, Ba)₂SiO₄:Eu and Ca₃Sc₂Si₃O₁₂:Ce,chlorosilicate phosphors such as Ca₈MgSi₄O₁₆Cl_(2-δ):Eu, Mn, oxynitridephosphors such as β-SIALON of (Ca, Sr, Ba)₃Si₆O₉N₄:Eu, (Ca, Sr,Ba)₃Si₆O₁₂N₂:Eu, (Ca, Sr, Ba)Si₂O₂N₂:Eu, CaSc₂O₄:Ce,Si_(6-z)Al_(z)O_(z)N_(8-z):Eu, etc., aluminate phosphor activated by Ce,such as (Y, Lu)₃(Al, Ga)₅O₁₂:Ce, and sulfide phosphors activated by Eu,such as SrGa₂S₄:Eu.

Examples of the phosphors for emitting blue light to be used togetherwith the phosphor according to this embodiment can be provided byaluminate phosphors activated by Eu, such as (Sr, Ca, Ba)Al₂O₄:Eu, (Sr,Ca, Ba)₄Al₁₄O₂₅:Eu, (Ba, Sr, Ca)MgAl₁₀O₁₇:Eu, and BaMgAl₁₄O₂₅:Eu, Tb,Sm, aluminate phosphors activated by Eu and Mn, such as (Ba, Sr,Ca)MgAl₁₀O₁₇:Eu, Mn, thiogallate phosphors activated by Ce, such asSrGa₂S₄:Ce and CaGa₂S₄:Ce, and halophosphate phosphors activated by Eu,such as (Sr, Ca, Ba, Mg)₁₀(PO₄)₆Cl₂:Eu.

(Sealing Member)

The sealing member 103 is formed of transparent resin or glass. Therecessed portion of the light-emitting apparatus 100 is filled with thetransparent resin or glass so that the light-emitting device 101 iscovered by the transparent resin or glass. In terms of ease ofproduction, the sealing member is preferably formed of transparentresin. A silicone resin composition or the like is preferably used asthe transparent resin. However, an electrically insulating resincomposition such as epoxy resin composition, acrylic resin compositionor the like can be also used. An additive member can be suitablyincluded together with the phosphor 102 in the sealing member 103. Forexample, a light diffusion member can be added to the sealing member. Inthis case, the directivity from the light emitting device can be reducedso that the viewing angle can be increased.

The following description will describe phosphors according to examples1 to 4 of the present invention. Lanthanum nitride (LaN), siliconnitride (Si₃N₄), praseodymium nitride (PrN), and cerium fluoride (CeF₃)are used as materials for the phosphors according to the examples 1 to4. The phosphors are obtained based on measurement of the materials atthe following preparation composition ratios. It should be appreciated,however, that the examples described below are illustrations of aphosphor and a phosphor production method to give a concrete form totechnical ideas of the present invention, and a phosphor and a phosphorproduction method of the present invention are not specifically limitedto the description below.

Example 1

In the example 1, the materials are measured at a preparationcomposition ratio of La:Si:Ce:Pr=3:6:0.15:0.0005. More specifically, thefollowing powder materials are measured as materials for the phosphoraccording to the example 1. Here, the purities of the materials for thephosphor are assumed 100%.

Lanthanum Nitride (LaN) . . . 5.97 g

Silicon Nitride (Si₃N₄) . . . 3.65 g

Praseodymium Nitride (PrN) . . . 0.001 g

Cerium Fluoride (CeF₃) . . . 0.38 g

The measured materials are sufficiently mixed in a dry manner, andplaced in a crucible. The materials are burned at 1,500° C. for 10hours. The burned product is pulverized and then placed in hydrochloricacid solution. Thus, phosphor powder is obtained.

Examples 2-4 and Comparative Example 1

Similar to the example 1, the materials are adjusted to the mixtureratios shown in the following Table 1, and phosphors according toexamples 2 to 4 and a comparative example 1 are obtained. The particlediameters, powder properties, intensities and the like are measured. InTable 1, Dm means particle diameter (μm). The particle diameters aremeasured by particle measurement using electric resistance based onaperture's electrical resistance method (electrical sensing zone method)as Coulter principle. More specifically, after the phosphors aredispersed in a solution, their particle diameters are obtained based onthe electric resistances that are produced when particles of thephosphors pass through an aperture of an aperture tube.

FIGS. 2 and 3 show the normalized light emission spectrums andexcitation spectrums of the phosphors according to the examples 1 to 4and the comparative example 1, respectively. FIG. 4 is a SEM image ofthe phosphor according to the example 4, magnified by 1,000 times. Table2 shows composition ratios obtained by an analysis apparatus. The symbol“-” in Table 2 shows that the analyzed value of Pr is smaller than thedetectable limit of the analysis apparatus. As shown in Table 1 and FIG.2, the light emission intensity ratios at wavelength 615 nm (I_(p615))of the phosphors according to the examples are higher than that of thephosphor according to the comparative example 1. In other words, the redlight component of the phosphors according to the examples is increasedas compared with the phosphor according to the comparative example 1.

The light emission intensities of the phosphors according to theexamples are relatively high substantially at wavelength 615 nm. Forthis reason, the red light component intensity is defined at wavelength615 nm in the examples. However, the red light component intensity isnot limited to wavelength 615 nm. For example, the red light componentintensity can be defined at a wavelength in a range from 610 to 620 nm,such as 610, 615, and 620 nm, for calculation of the light emissionintensity ratio to evaluate increase in red light component.

Also, the light emission intensities of the phosphors are the highest atwavelength 535 nm in their spectrums. For this reason, the red lightcomponent intensity is defined relative to the light emission intensityat wavelength 535 nm. However, the red light component intensity can bedefined relative to the intensity at another wavelength other than 535nm for calculation of the light emission intensity ratio to evaluateincrease in red light component.

In light-emitting apparatuses that include the phosphors according tothe examples and the light-emitting device, it can be confirmed that thecolor rendering property and the color reproduction range are improved.As shown in FIG. 3, it can be confirmed that the phosphors according tothe examples are efficiently excited by blue light in a wavelength rangefrom 420 to 470 nm. Also, as shown in Table 1 and FIG. 4, it isconfirmed that the phosphors have particle diameters in a range from 2to 30 μm.

TABLE 1 Intensity Particle Powder Properties Ratio Dia. RelativeIntensity 615 nm/ Sample La Si Ce Pr Dm x y Intensity 535 nm 615 nm 535nm Comp. Ex. 1 3 6 0.15 0 18.3 0.419 0.557 100.0 99.2 55.8 0.56 Ex. 10.0005 15.8 0.419 0.556 95.4 94.3 54.2 0.58 Ex. 2 0.001 13.7 0.420 0.55695.0 93.9 55.7 0.59 Ex. 3 0.003 18.7 0.424 0.553 93.8 92.3 60.0 0.65 Ex.4 0.01 8.3 0.422 0.551 76.1 73.9 50.8 0.69

TABLE 2 Composition Analyzed Value (Base on Analyzed Value) (ppm) SampleLa Si Ce Pr N F O Comp. Ex. 1 2.66 6.00 0.13 — 10.70 1200 1020 Ex. 12.58 6.00 0.13 0.0005 10.40 740 2010 Ex. 2 2.60 6.00 0.13 0.0009 10.421500 1820 Ex. 3 2.65 6.00 0.13 0.0044 10.76 1500 1310 Ex. 4 2.69 6.000.16 0.0148 10.92 1700 4550

Example 5 and Comparative Examples 2-3

Relative intensities and the like of phosphors according to an example 5and comparative examples 2 to 3 are measured which have differentcomposition ratios of La on the basis of the phosphor according to theexample 4. The measured values of the phosphors according to the example5 and the comparative examples 2 to 3 are shown in Tables 3 to 4, andFIGS. 5 to 6. Also, similar to the example 1, etc., the materials areadjusted to the mixture ratios shown in the Table 3, and the phosphorsaccording to the example 5 and the comparative examples 2 to 3 areobtained. The particle diameters, powder properties, intensities and thelike are measured. Similar to Table 1, Dm is an index of particlediameter (μm) in Table 3. Also, FIGS. 5 and 6 show the normalized lightemission spectrums and excitation spectrums of the phosphors accordingto the example 5 and the comparative examples 2 to 3, respectively.Table 4 shows composition ratios obtained by the analysis apparatus. Asshown in Table 3 and FIG. 5, the relative intensity of the phosphoraccording to the example 5 is higher than those of the comparativeexamples 2 to 3. In other words, it can be confirmed that the relativeintensity of the phosphor according to the example 5 is improved.According to this result, when the compounding ratio of La is not higherthan 2 or not lower than 3.5, the relative intensity of the phosphorremarkably decreases. For this reason, it is preferable that thecompounding ratio of La be higher than 2 and lower than 3.5. As shown inFIG. 6, it can be confirmed that the phosphor according to the example 5is efficiently excited by blue light in a wavelength range from 420 to470 nm.

TABLE 3 Particle Powder Properties Intensity Dia. Relative IntensityRatio Sample La Si Ce Pr Dm x y Intensity 535 nm 615 nm 615/535 Comp.Ex. 2 2 6 0.15 0.01 10.1 0.423 0.548 19.4 19.0 13.3 0.70 Ex. 5 2.5 12.60.426 0.550 48.8 47.6 35.0 0.73 Ex. 4 3 8.3 0.422 0.551 76.1 73.9 50.80.69 Comp. Ex. 3 3.5 21.2 0.432 0.541 31.4 29.0 24.0 0.83

TABLE 4 Composition Analyzed Value (Analyzed Value) (ppm) Sample La SiCe Pr N F O Comp. Ex. 2 1.89 6.00 0.14 0.0110 9.88 2600 4500 Ex. 5 2.146.00 0.12 0.0115 10.06 2100 4260 Ex. 4 2.69 6.00 0.16 0.0148 10.92 17004550 Comp. Ex. 3 2.20 6.00 0.10 0.0146 7.70 11000 85430

Examples 6-7 and Comparative Example 4

Relative intensities and the like of phosphors according to examples 6to 7 and a comparative example 4 are measured which have differentcomposition ratios of Ce on the basis of the phosphor according to theexample 4. The measured values of the phosphors according to theexamples 6 to 7 and the comparative example 4 are shown in Tables 5 to6, and FIGS. 7 to 8. Also, similar to the example 1, etc., the materialsare adjusted to the mixture ratios shown in the Table 5, and thephosphors according to the examples 6 to 7 and the comparative example 4are obtained. The particle diameters, powder properties, intensities andthe like are measured. Also, FIGS. 7 and 8 show the normalized lightemission spectrums and excitation spectrums of the phosphors accordingto the examples 6 to 7, and the comparative example 4, respectively.Table 6 shows composition ratios obtained by the analysis apparatus. Asshown in Table 5 and FIG. 7, the relative intensities of the phosphorsaccording to the examples 6 to 7 are higher than that of the comparativeexample 4. In other words, it can be confirmed that the intensities ofthe phosphors according to the examples 6 to 7 are improved. Accordingto this result, when the compounding ratio of Ce is not smaller than 1,the relative intensity of the phosphor remarkably decreases. For thisreason, it is preferable that the compounding ratio of Ce be smallerthan 1. As shown in FIG. 8, it can be confirmed that the phosphoraccording to the example 5 is efficiently excited by blue light in awavelength range from 420 to 470 nm.

TABLE 5 Particle Powder Properties Intensity Dia. 615/ Intensity RatioSample La Si Ce Pr Dm x y 535 535 nm 615 nm 615/535 Ex. 6 3 6 0.05 0.0115.8 0.410 0.559 65.5 64.2 37.4 0.58 Ex. 4 0.15 8.3 0.422 0.551 76.173.9 50.8 0.69 Ex. 7 0.3 23.0 0.440 0.542 76.4 72.9 59.0 0.81 Comp. Ex.4 1 14.3 0.465 0.521 34.9 30.4 33.9 1.12

TABLE 6 Composition Analyzed Value (Analyzed Value) (ppm) Sample La SiCe Pr N F O Ex. 6 2.57 6.00 0.05 0.0040 10.14 1800 1240 Ex. 4 2.69 6.000.16 0.0148 10.92 1700 4550 Ex. 7 2.54 6.00 0.22 0.0111 10.98 590 980Comp. Ex. 4 1.91 6.00 0.70 0.0074 10.59 3300 1290

Light-Emitting Apparatus Using Phosphors of Comparative Example 1 andExample 3

The results of light-emitting apparatuses including the phosphorsaccording to the comparative example 1 and the example 3 are shown inTable 7 and FIGS. 9 to 10. The light-emitting apparatuses including thephosphor according to the comparative example 1 shown in the Table andFigures includes a phosphor for emitting red light in addition to thephosphor according to the comparative example 1. As shown in Table 7,CaAlSiN₃:Eu is used as a red phosphor in the comparative example 1.Contrary to this, the light-emitting apparatus including the phosphoraccording to the example 3 does not include the red phosphor. Thelight-emitting device is an LED device that has a size 500×290 μm, andemits light in a blue range with peak wavelength of 450 nm. The lightemitting apparatus includes the LED device, and silicone resin thatcontains the phosphor and covers the LED device. FIG. 9 is a graphshowing the light emission spectrums of the light-emitting apparatuses.FIG. 10 is an enlarged graph of a range from 0 to 1,500 in lightemission intensity in FIG. 9. As shown in FIGS. 9 to 10, it can beconfirmed that, although the light-emitting apparatus including thephosphor according to the example 3 does not include the red phosphor,its luminous flux ratio is relatively high, and is almost the same asthe light-emitting apparatuses including the phosphor according to thecomparative example 1. Since the aforementioned light-emitting apparatusincludes only one type of phosphor according to the example, it ispossible to reduce color unevenness, which may occur in a light-emittingapparatus including two or more types of single phosphors. In additionto this, it is confirmed that the aforementioned light-emittingapparatus include only one type of phosphor according to the example hasgood optical properties.

TABLE 7 Red Fwd. Cur. Fwd. Vltg Luminous Chroma- Chroma- Phosphor (mA)(V) Flux Ratio ticity x ticity y Comp. Ex. 1 CaAlSiN₃:Eu 150 3.3 1000.266 0.236 Ex. 3 — 150 3.3 99.4 0.265 0.236

As discussed above, it can be found that the phosphors according to theexamples are efficiently excited by light having a main peak in a rangefrom near-ultraviolet to blue light, and have a first peak in a rangefrom 515 to 545 nm in their light emission spectrums. In addition, itcan be found that the light emission intensity of these phosphors inproximity to 615 nm is not smaller than 56% of the light emissionintensity at the first peak, and these phosphors can efficiently emit ared light component. If the amount of Pr added to the phosphor falls outof the range that does not allow the phosphor to emit light at the abovelight emission intensity ratio, the light may include an insufficientred light component. In the case where a light-emitting apparatusincludes the phosphor according to the present invention together with alight-emitting device that emits light in a range from near-ultravioletto blue light, the light-emitting apparatus can have a high lightemission efficiency, good color rendering property, and good colorreproduction range. In addition to this, in the case where alight-emitting apparatus includes an additional phosphor, it will bepossible to further improve the light emission spectrum of thelight-emitting apparatus. In this case, the amount of the additional redphosphor can be reduced. The reason is that the light emission intensity(I_(p615)) at 615 nm can be increased so that the red light componentcan be increased in the light-emitting apparatus. Alternatively, theadditional red phosphor may not be required in the light-emittingapparatus. It is preferable that the composition ratio of the amount ofPr added to the phosphor fall within a range between 0 and 0.05.

A phosphor, a light-emitting apparatus including the phosphor, and aphosphor production method according to the present invention can beused for a white lighting source, LED display, back light source, signallight, illuminated switch, various sensors, various indicators, and thelike that have a light source of a blue or ultraviolet light-emittingdiode with good light emission properties. In particular, the phosphoraccording to the present invention can reduce color unevenness, and bereliable. Therefore, the phosphor according to the present invention hasgreat value in industry.

It should be apparent to those with an ordinary skill in the art thatwhile various preferred embodiments of the invention have been shown anddescribed, it is contemplated that the invention is not limited to theparticular embodiments disclosed, which are deemed to be merelyillustrative of the inventive concepts and should not be interpreted aslimiting the scope of the invention, and which are suitable for allmodifications and changes falling within the scope of the invention asdefined in the appended claims. The present application is based onApplications No. 2013-94771 filed in Japan on Apr. 26, 2013, and No.2014-7917 filed in Japan on Jan. 20, 2014, the contents of which areincorporated herein by references.

Throughout the present specification, where compositions, apparatuses orprocesses are described as including or comprising specific components,or materials, or steps, it is contemplated by the inventors thatcompositions, apparatuses or processes of the present invention alsoconsist essentially of, or consist of, the recited components,materials, or steps. Accordingly, throughout the present disclosure anydescribed composition, apparatus or process of the present invention canconsist essentially of, or consist of, the recited components,materials, or steps.

What is claimed is:
 1. A phosphor represented by the general formulaM_(x)Ce_(y)Pr_(z)Si₆N_(8+w), wherein M is at least one element selectedfrom the group consisting of La, Y, Tb and Lu, wherein 2.0<x<3.5,0<y<1.0, 0<z<0.05, and 2.0<w<4.0.
 2. The phosphor according to claim 1,wherein 2.0<x<3.0, 0<y<0.5, and 0<z<0.03.
 3. The phosphor according toclaim 1, wherein said phosphor can absorb light in a range fromultraviolet light to visible blue light and emit light different fromthe absorbed light, wherein the light emitted by said phosphor has alight emission spectrum including first and second peaks, and whereinthe wavelengths of the first and second peaks fall within ranges from515 to 545 nm, and 610 to 620 nm, respectively.
 4. The phosphoraccording to claim 3, wherein the light emission intensity ratio(I_(p2)/I_(p1)) of the second peak relative to the first peak is definedin said emission spectrum, wherein 0.56<I_(p2)/I_(p1).
 5. The phosphoraccording to claim 1, further containing 10 to 10,000 ppm of fluorine.6. The phosphor according to claim 1, further containing 100 to 10,000ppm of oxide.
 7. The phosphor according to claim 1, said phosphorcomprising a crystal phase, wherein the percentage of the crystal phaseis not less than 50% by weight.
 8. A light emitting apparatus,comprising: an excitation light source that can emit light in a rangefrom ultraviolet to blue light; the phosphor according to claim 1 as afirst phosphor that can absorb a part of the light from said excitationlight source, and can emit luminescent radiation; and a wavelengthconversion member in which said first phosphor is distributed.
 9. Thelight emitting apparatus according to claim 8, further comprising atleast one second phosphor that can absorb at least a part of the lightfrom said excitation light source, and can emit luminescent radiationwith a peak wavelength different from that of said first phosphor.
 10. Aphosphor production method, comprising: preparing, pulverizing andmixing materials for elements to compose a composition of phosphor, thematerials including the elements themselves, or oxide, nitride orcarbonate of the elements, so as to provide obtained materials; fillinga crucible with the obtained materials, and burning the obtainedmaterials in a reducing atmosphere, so as to form a burned product;subjecting the burned product to solid-liquid separation, and drying,pulverizing, dispersing and filtering the product after the solid-liquidseparation, thereby obtaining phosphor powder, wherein said compositionof phosphor is represented by the general formulaM_(x)Ce_(y)Pr_(z)Si₆N_(8+w), wherein M is at least one element selectedfrom the group consisting of La, Y, Tb and Lu, wherein 2.0<x<3.5,0<y<1.0, 0<z<0.05, and 2.0<w<4.0.
 11. The phosphor production methodaccording to claim 10, wherein the burned product is placed in an acidsolution, thereby reducing the content of impurities contained in theburned product.
 12. The phosphor production method according to claim11, wherein said acid solution contains hydrochloric acid.
 13. Thephosphor production method according to claim 10, wherein said materialscontain fluoride.